The search for the molecular mechanisms underlying tumorigenesis has focused on the signal transduction pathways within cells. With respect to adult brain tumors, recent research has identified two ligand/receptor systems that may be important in the genesis of a wide variety of these tumors. These are the TGF-alpha/EGF receptor and the PDGF/PDGF receptor. Each of these components has been found to be inappropriately expressed or altered in tumors. Unfortunately, the methods used to study adult brain tumors has not been extensively applied towards pediatric brain tumors. The studies to date suggest that such an approach could lead to significant discoveries for pediatric medulloblastoma. In the first part of this proposal, such tumors will be analyzed for expression of TGF-alpha, PDGF and PDGF receptor by using Western blots with a specific antibody. Amplification and alteration of the EGF receptor, which is the most frequent molecular genetic change in adult brain tumors, will also be examined in medulloblastoma. Both the EGF and PDGF receptor interact with the gamma form of phospholipase C (PLC-gamma). We have found that PLC-gamma can transform cells and is preferentially expressed in many tumors. It is planned to see if this is true for medulloblastoma by using Western blots to determine the relative amounts of PLC-gamma vs PLC-beta or PLC-delta. IP3, one of the enzymatic products, levels will be assayed to see if this correlates with enzyme levels. Immunohistochemistry will be performed to determine whether this protein might be useful for diagnostic purposes. Southern blots will be employed to screen for any potential alterations within the gene. PLC- gamma can also specifically interact with proteins and we will use bacterially synthesized fusion proteins to identify novel associations with PLC-gamma. It is anticipated that these studies will reveal whether growth factors, their receptors and PLC-gamma play any role in the pathogenesis of these tumors. Additionally, information about the expression of these proteins may be used to improve diagnosis. We have already shown for adult brain tumors that altered EFG receptors represent unique targets for tumor specific antibodies.